The present invention relates to an image processing apparatus and, more particularly, to an image processing apparatus for compressing and expanding an image data.
When digital image data is exchanged through a communication line or is stored in a storage device, the data is compressed to reduce the load imposed on the communication line or the storage device. Image compression techniques utilized by the present invention include lossless compression and lossy compression. When lossless compression is used, the compressed image can be perfectly decoded to an original image by using a run-length recording technique or a compression technique for coding by use of the Huffman method, after redundant data is compressed by forecast encoding. In contrast to this, the lossy compression technique has a higher compression ratio than that of the lossless compression technique. However, this technique cannot perfectly decode the compressed image data to an original image, and the image quality is degraded in proportion to the compression ratio.
When the image processing apparatus is used for medical diagnosis, a very high quality image is required. Consequently, lossless compression, which involves no degradation, is the technique used in the field o medicine. For this reason, the compression ratio for the medical image cannot be greatly improved, and the storage used for storing the medical image cannot be reduced in storage capacity.